@JsonProperty
  protected MongoConfiguration mongoA;
  @JsonProperty
  protected MongoConfiguration mongoB;

  public MongoConfiguration getMongoA() {
    return mongo;
  }

  public MongoConfiguration getMongoB() {
    return mongo;
  }

MongoBundle<ExampleConfiguration> mongoBundleA;
MongoBundle<ExampleConfiguration> mongoBundleA;

@Override
public void initialize(Bootstrap<ExampleConfiguration> bootstrap) {
  bootstrap.addBundle(mongoBundleA = MongoBundle.<ExampleConfiguration>builder()
    .withConfiguration(ExampleConfiguration::getMongoA)
    .build());
  bootstrap.addBundle(mongoBundleB = MongoBundle.<ExampleConfiguration>builder()
    .withConfiguration(ExampleConfiguration::getMongoB)
    .build());
}

import com.mongodb.MongoCredential;

// ...

String user;        // the user name
String database;    // the name of the database in which the user is defined
char[] password;    // the password as a character array
// ...
MongoCredential credential = MongoCredential.createCredential(user,
                                                             database,
                                                              password);

  Optional.ofNullable(credentialConfig.getAuthenticationDatabase()).orElse(configuration.getDatabase())